1. Field of the Invention:
This invention relates to water-soluble temper rolling oil and a method of temper rolling using the same.
2. Description of the Prior Art:
In general, a cold rolled carbon steel sheet is manufactured by pickling hot rolled steel and then subjecting the pickled hot rolled steel to a series of steps, i.e., cold rolling, annealing and temper rolling. In conducting the temper rolling, a temper rolling oil is used. This temper rolling oil is desired to not only have an appropriate lubricity, detergency sufficient to wash metal wear debris formed, and excellent rust preventive properties, but also to permit uniform application of a final rust preventive oil in a subsequent step that is inexpensive.
Examples of conventional temper rolling oils include an aqueous solution composed mainly of sodium nitrite and alkanolamine having excellent rust preventive properties and an aqueous solution containing at least two alkali metal salts of organic acids such as aliphatic monocarboxylic acid, hydroxycarboxylic acid, aliphatic dibasic acid, benzoic acid, and a nitro group- or amino group-substituted benzoic acid, as disclosed in the laid-open Japanese patent publication Nos. 56-81397, 59-1686, and 60-255896. In recent years, it has been required that, in addition to the above-mentioned properties, the temper rolling oil imparts advanced properties, such as (1) high lubricity, (2) high gloss, (3) apparent dryness of the surface of the sheet, and (4) excellent direct paintability.
Specifically, the temper rolling by making use of bright rolls has been conducted using the conventional temper rolling oil at a reduction ranging from 0.5 to 5%. However, in order to impart special properties to materials, it is often necessary to conduct the temper rolling at a reduction exceeding 5% and up to 30%.
In the conventional temper rolling oils, difficulties were encountered in conducting high reduction temper rolling at a reduction exceeding 10%. Further, even in the case of the temper rolling at a reduction of 5% or less, the conventional temper rolling oil brought about a jumping phenomenon. Therefore, no consistent correlation could be attained between the load and the elongation percentage of the steel sheet, which made it difficult to adjust the elongation percentage through increase or decrease in the load.
Moreover, temper rolling at a high reduction cannot be conducted using the conventional temper rolling oils, which leads to the drawback that conventional temper rolling oils cannot produce a sheet having a high surface gloss.
In temper rolling by making use of either bright rolls or dull rolls, the conventional temper rolling oils provided apparent wetness with respect to the surface of the steel sheet, i.e., and appearance as if an oil adhered thereon, which made it impossible to give apparent dryness. Further, when the conventional temper rolling oils were used, no good adhesive property of a coating could be obtained unless the adherent was removed in a washing step when practicing the coating of the steel sheet.
The present inventors have made extensive and intensive studies with a view to developing a temper rolling oil capable of providing a steel sheet having the above-metioned additional properties as well. This led to an invention as described in the laid-open Japanese patent publication No. 61-7395 which relates to a temper rolling oil comprising of a water-soluble cationic compound, prepared by neutralizing a condensation product composed of a specific aliphatic dibasic acid and a specific polyamine with an oxoacid of phosphorus, in a concentration of 300 to 5,000 ppm. This invention contributed to the attainment of the above-mentioned purpose of imparting advanced properties such as (1) high lubricity, (2) high gloss, (3) apparent dryness of the surface of the sheet, and (4) excellent direct coating properties.
However, since in the temper rolling oil as described in the laid-open Japanese patent publication No. 61-7395, the number of basic nitrogen atoms contained in the condensation product which forms an essential component, i.e., and aqueous cationic compound, is small, the condensation product becomes water soluble when it is neutralized with an acid of phosphorus. However, the use of the temper rolling oil in combination with the above-mentioned rust preventive component leads to a remarkable decrease in the water solubility. For this reason, in the case of the temper rolling oil as described in the above-mentioned laid-open publication, the allowable maximum amount of addition of a rust preventive component was as small as about 1,000 ppm, and the addition in an amount exceeding this allowable limit brought about precipitation of the lubricating component, i.e., water-soluble cationic compound, which lowered the concentration thereof. This in turn caused not only a decrease in the effect attained therefrom but also to the occurrence of glossy spots called mottling because precipitated water-insoluble matter intruded between the steel sheet and the rolls. When the temper rolling was conducted using this temper rolling oil and bright rolls at a relatively high reduction, water was sufficiently drained off, so that a rolled coil was free from rusting even during its storage. On the other hand, the temper rolling at a low reduction or the temper rolling by making use of dull rolls brought about insufficient draining of water, which in turn led to occurrence of spotted rust during storage of a rolled coil.